<h3>tri-state checkboxes</h3>
<tree-root
  id="tree1"
  [nodes]="nodes"
  [options]="options">
</tree-root>
<h3>The tree is using flexbox.<br>
  Switch expander and checkbox with CSS 'order' attribute:</h3>
<tree-root
  class="reverse"
  id="tree2"
  [nodes]="nodes"
  [options]="options">
</tree-root>
<h3>Disable tri-state checkboxes</h3>
<tree-root
  id="tree3"
  [nodes]="nodes"
  [options]="optionsDisabled">
</tree-root>
